It is faster if you stand on the escalators
As State tells us in its article: Don’t Walk on Escalators. It’s Faster if Everyone Stands.
A survey from the Greenwich University in 2011 found out that 75% of the people from the metro do not walk when they are at the escalators while the other 25% do. Firstly, we can easily see that set apart half the escalator for only the 25% of the people does not make too sense. In addition, people usually keep more distance when they are walking than when they are still.
So it seems this is a studied issue that has been simulated many times, and with always the same conclusion: If everyone stands still, the escalator can take on more passengers per minute.
For instance, the simulations made by “Transport of London” determine that an escalator full of stopped people is able to carry 112,5 people per minute. And the same escalator with 2 queues, one for whom are walking and other for the stopped people, makes the flux decreases to 81,25 people per minute.
More recently, a real test confirmed the simulation results: For some weeks, the London metro workers were forcing the passengers to keep still on the escalators. Well, they tried to do as much as they could, asking kindly to stay still, or even blocking the way with couples holding hands, and other ruses to block the walkers.
Although it was impossible to stop everybody, the result pointed that the same escalator which used to carry 12.745 people per hour (at rush hour), was able to carry 16.220 people within the same time.
The problem, of course, is that an individual person goes faster when he walks on the escalator. In fact, it turns impossible and complicated not to walk for many people, especially if they are in a hurry.
More details about it at The Guardian: The tube at a standstill: why TfL stopped people walking up the escalators.